This invention relates to a casing structure for electrical and mechanical units, and, more particularly, to a casing structure consisting of a main or first casing unit and a sub or second casing unit connected to the first casing unit by hinge members.
A casing structure comprising a casing body and a door of relatively light weight which is connected to the casing body by hinge members is well known. However, it is not appropriate to accommodate some units, such as a line printer, into a casing structure of the above-mentioned type, since a line printer has some mechanical and electrical units accommodated in a main casing, as well as a printing sheet stacked section in front of the main casing and a printed sheet discharging or stacked section at the rear side in the casing. Therefore, the casing required would be of a relatively large volume, so that, if such a casing were constructed as a single casing unit, a large space in the casing would be occupied by the above-mentioned printing and printed sheet stacked sections. Consequently, only a small space in the casing could be used for the important mechanical and electrical units, thereby allowing no space for maintaining and repairing these units.
A casing structure comprising a main casing and a sub casing separable or hingedly connected to each other is also well known. In a type of casing structure wherein the sub casing is mounted on the main casing by means of screws or connected thereto by hinge members, the sub casing is too heavy to manipulate by operators or the main casing is otherwise subjected to the heavy weight of the sub casing. In addition, this type of casing is unstable because of the heavy weight of the sub casing, so that the center of gravity is moved toward the sub casing when the latter is opened.
A casing structure similar to the previous mentioned type is known wherein the sub casing has support rollers or casters on the bottom thereof. With this type of casing, it is easy to manually operate the sub casing due to the supporting rollers. However, it is sometimes difficult to keep the supporting legs or casters of the main casing and the above-mentioned supporting rollers of the sub casing level, since the floor on which the casing structure is situated is not flat in a strict sense. Therefore, it is sometimes necessary to adjust the level of the supporting legs or casters of the main casing everytime the casing structure is relocated.
In the above-mentioned casing structures, it is also difficult to electrically connect for the ground between the main and sub casing units due to an electrostatic shield. Using several lines for this purpose causes a slight electrical noise.
In a casing structure accommodating a line printer, for example, it is usually necessary to cool the various parts thereof, since the line printer comprises: mechanical units, such as a printing magnet, a sheet feeding motor, printing type belts, a ribbon driving motor, and various control magnets; and electrical units, such as a power unit, rectifier and stabilizing circuits, magnet driving circuits, a sheet feeding motor driving circuit; and various control magnets and ribbon driving circuits. All of these mechanical and electrical units may be sources of heat generation. A casing structure is, therefore, usually provided with a power cooling fan at the inside of the casing and cooling air inlet and outlet ducts. In some cases, the air inlet and outlet ducts are also provided with cooling fans, respectively, in order to attain compulsory air circulation.
A casing structure has another important role as a soundproofing cover, since impact sounds are generated from the printing unit, while a printing hammer blows the types against printing sheets. However, a casing structure having air cooling inlets and outlets does not perform effective soundproofing, because the impact sounds tend to leak outside through the cooling air inlet and outlet openings. If foam rubber or some other suitable soundproofing material is provided on the inner walls of the casing in order to obtain effective soundproofing, effective heat radiation would be reduced due to these soundproofing materials. Therefore, some casing structures are provided with special mufflers, which, however, require extra space and increase costs.